Which of the following written documents typically offers the best evidence that internal auditors exercise due professional care in conformance with the Standards?

Workpapers (also known as engagement records) are the primary documentation of the audit process. They contain the detailed records of planning, risk assessments, procedures performed, evidence gathered, and conclusions reached. This comprehensive documentation serves as the principal evidence that the internal auditor exercised due professional care by demonstrating a diligent, competent, and systematic approach in conformance with the International Standards for the Professional Practice of Internal Auditing (specifically Standard 1220: Due Professional Care and Standard 2330: Documenting Information).

A. Internal audit charter: The charter is a high-level document that defines the internal audit activity's purpose, authority, and responsibility; it does not provide evidence of care exercised during a specific engagement.
C. Audit report: The audit report is a summary of the engagement's results and conclusions. It is the product of the audit work, not the detailed evidence of the process followed to achieve it.
D. Code of ethics: The code of ethics provides guiding principles and rules of conduct for auditors. It is a framework for behavior, not evidence of the actual performance or diligence in an audit. ---

1. The Institute of Internal Auditors (IIA). (2017). International Standards for the Professional Practice of Internal Auditing.

Standard 1220: Due Professional Care: "Internal auditors must apply the care and skill expected of a reasonably prudent and competent internal auditor." This standard sets the requirement.

Standard 2330: Documenting Information: "Internal auditors must document relevant information to support the conclusions and engagement results." The Interpretation section clarifies that engagement workpapers "provide the principal support for the internal auditors’ communications" and "facilitate quality assurance reviews," which would assess due professional care.

2. Pickett, K. H. S. (2011). The Internal Auditing Handbook (3rd ed.). John Wiley & Sons.

Chapter 18, "Working papers," explains that workpapers are essential to demonstrate that the audit was performed with due professional care and in accordance with professional standards. They provide the evidence linking the audit objectives to the conclusions. (Specific reference: pp. 485-487).

3. Moeller, R. R. (2016). Brink's Modern Internal Auditing (8th ed.). John Wiley & Sons.

Chapter 13, "Performing the Internal Audit Engagement," states, "Audit working papers are the records kept by the internal auditor of the procedures followed, the tests performed, the information obtained, and the conclusions reached... They provide the evidence that the internal auditor has exercised due professional care." (Specific reference: Section on "Documenting Internal Audit Work").